Enhanced water monitoring one step closer

New water monitoring systems now in place in Te Waihora/Lake Ellesmere are expected to improve the overall management of the lake.

Senior Hydrological Officer for Environment Canterbury, Alex Ring says the new systems will provide a deeper understanding of the lake.

“These new tools will give us a better understanding of changes happening within the lake. We will get a much better grasp on why things like algal blooms happen for instance. We’ll be able to look at the water temperature at the base of the lake or the salinity of the water for example to help us determine what may have spiked the bloom,” he says.

“Being able to look at changes in the lake over time and being able to feed that data into specific models, will have important implications for our lake management tools.”

To this point, water quality monitoring in Te Waihora consisted of monthly samples and measurements taken at four sites around the lake. These samples were sent to a laboratory for analysis of a range of attributes. Two conductivity meters in the lake also provided continuous records that were downloaded at the same time as the samples were taken.

“The new systems will provide a deeper understanding of the lake.”

According to Alex Ring, that type of monitoring was good for detecting long term changes in water quality parameters and for deriving a lake trophic level index (TLI) but it tells us very little about short term changes in water quality. He says Whakaora Te Waihora science research on nutrient processing by a team lead from the University of Otago, highlighted the fact that short term changes in dissolved oxygen and other parameters were important for understanding and managing the lake.

The two new telemetered water quality monitoring stations complement the two conductivity meters in the mid-lake area and near the lake opening at Taumutu. Alex says the central lake position is indicative of the lake as a whole, while the lake opening site – the most dynamic part of the lake – was chosen as a case study because of the large inputs of saltwater in the area.

“We wanted to see the difference between these two areas and to see the effect of those dynamics within a localised area.”

The new equipment is designed to monitor beam transmission (a clarity measurement); dissolved oxygen in the water (one at lake bottom and one at the top); water acidity (PH); temperature throughout the water column; conductivity and salinity; turbidity and fluorescence (algal concentrations). The technology included in the system then relays the data, via telemetry – back to Environment Canterbury in Christchurch every two or three hours.

Meteorological conditions including air temperature, barometric pressure, relative humidity, wind speed and direction and solar radiation are also measured.

The monitors located near the lake opening. The settlement of Taumutu is seen in the rear.

“There were a few challenges in getting the equipment installed due to unsuitable weather conditions but I’m very happy with the way everything has come together. It’s gone well, thanks in no small part to Chris McBride of the University of Waikato. Chris has done a great job of setting up the sensors and data-loggers which has made the set-up process much easier. They have been designed to withstand whatever is thrown at them, and so far they have survived some very strong winds.

Alex says that in coming months, that information will be displayed on the Environment Canterbury website for any interested stakeholders to view.

“Adding these new monitoring stations provides a rare opportunity to greatly enhance our scientific understanding of the short term variations and processes in water quality. The new data we’re getting fills in a lot of gaps. It’s much more comprehensive and gathered at a greatly increased frequency, so it will be a powerful tool in modelling all sorts of scientific research, as well as tracking the health of the lake” he says.